1. Field of the Invention
This invention relates to a microscope adapted for use in surgery, for example.
2. Description of the Prior Art
Heretofore, there has been a microscope for magnifying a diseased part and observing it stereoscopically in surgery.
FIG. 5 is a schematic view showing the construction of a conventional microscope. This microscope comprises a first objective optical system 1 and a second objective optical system 2, and a first ocular optical system 3 and a second ocular optical system 4. The first ocular optical system 3 includes an eyepiece 3a and the second ocular system 4 includes an eyepiece 4a. The first objective optical system 1 includes an objective lens 5, an image-formation lens 6, an erecting prism 7, and a reflecting prism 8, and the second objective optical system 2 includes the objective lens 5, an image-formation lens 9, an erecting prism 10, a reflecting prism 11. Additionally, each of the objective optical systems 1, 2 includes a focussing lens (not shown).
In the conventional microscope constituted as mentioned above, image I1, I2 are formed in space by the first and the second objective optical systems 1,2 respectively, and magnified and observed by the ocular optical systems 3, 4, respectively.
In other words, the conventional microscope has optical coupling between the first and second objective optical systems 1, 2, respectively, and the first and second ocular optical systems 3, 4, respectively.
The optical coupling consequently yields a mechanical coupling between an objective lens barrel B which is constituted by the first and second objective optical systems 1, 2, and eyepiece barrels T1, T2 which are constituted by the first and second ocular optical systems 3, 4, as shown in FIG. 6. A length .alpha. between the eyepiece-barrels 3a, 4a and the objective lens 5 of the objective lens barrel B is fixed, and focussing is adjusted by a focussing lens (not shown). An observed part P (the diseased part, for example) can be well focussed by the focussing lens even though a working distance L between the objective lens 5 and the observed part P is determined arbitrarily. The working distance L is set by moving the lens barrel B up or down by rotating an arm A.
However, the long working-distance L is required because sufficient working-space required for surgery makes an operating distance M between the eyepiece 3a, 4a and the observed part P long. Because the object lens barrel B is mechanically coupled with the eyepiece barrels T1, T2, moving the object lens-barrel B upwardly away from the observed part P by rotating the arm A makes the eyepiece-barrels T1, T2 move upwardly at the same time. The long operating-distance M would cause the observer to make unnatural motions. In an extreme case, the observer's hands cannot reach the observed part P.
On the other hand, there has been a problem that the short operating-distance M by moving the lens-barrel B downwardly toward the observed part P due to the observer's small physique, for example, results in the short working-distance L, which would in turn cause the lens barrel B to obstruct surgical operations.